[llvm] [AMDGPU] Add backward compatibility layer for kernarg preloading (PR #119167)

[Janek van Oirschot via llvm-commits]

================
@@ -0,0 +1,229 @@
+//===- AMDGPUPreloadKernargHeader.cpp - Preload Kernarg Header ------------===//
----------------
JanekvO wrote:

Perhaps dumb question, what's being referred to as Header in this context? Is it similar/the same as the llvm loop terminology of a header?

https://github.com/llvm/llvm-project/pull/119167